Present invention relates to a sealing arrangement comprising two separate armature members and a sealing ring interposed therebetween and a clamping device for clamping the armature members against each other causing the intermediate sealing ring to be loaded with a sealing force, said sealing ring being made of metal or similar material and having a substantially T-shaped annular cross-section, said T-shape being provided with two in opposite axial direction extending sealing wings, each with an radially outwards facing sealing face and therebetween a central, rather rigid stem extending radially outwards and being provided with a combined gliding and support face to be supported against a counter face in the sealing arrangement, each of said sealing faces being conically shaped to be supported against a radially surrounding, correspondingly conically shaped gliding and support face in a corresponding armature member, each of said conical support faces of said armature members extends under a first, smallest cone angle, whereas each of said said sealing wings extends under a second, greatest cone angle, prior to mounting, and after mounting extends under said first cone angle to form a tight sealing abutment against its corresponding support face.
The present invention finds its application in a series of different areas of use, that is to say during moderate working conditions as well as during extreme working conditions.
The expression “ armature members” is employed herein for indicating that there are under discussion various types of “armature”. In the present embodiment however the invention is illustrated in connection with an armature in the of a pipe coupling.
During moderate working conditions there can be employed for example a sealing ring of rigid plastic or another suitable material, while under extreme working conditions, for example in a pipe coupling, there can be employed according to the illustrated embodiment a metallic sealing ring.
It is generally known to employ a metallic sealing ring of T-shaped annular cross-section in an intermediate space between two opposite coupling pieces of a pipe coupling. Such a pipe coupling can be used for example when high pressure and tensile loadings occur axially in the pipe coupling and when at the same time extreme internal medium pressure can occur in the joint between the coupling pieces/the armature members. In what follows “coupling piece ”will be indicated as armature member.
An example of such a known solution is shown in NO 178 388. Therein it is shown that the stem of the T-shape is clamped together via opposite side faces, in the axial direction of the pipe coupling, at the same time as laterally directed sealing flaps of the T-shape are clamped each via its cone face in the axial direction and radial direction of the pipe coupling for sealing abutment against a respective cone face of a stopper of a respective armature member.
An other example of such known solution is shown in AU 392 143. It is suggested therein that the sealing faces of the sealing wings of the sealing ring has a cone angle of 1°–2° steeper than that of the support face of the armature members. This will or may result in permanent deformation of the sealing ring in cases wherein the sealing faces are loaded with extreme pressure load. In practice this will involve that the sealing ring during mounting or hence during use is over-loaded and destroyed by exceeding the yield point of the metallic sealing ring and the latter is to be shifted. This will involve a time consuming and expensive shifting operation, especially in oil and gass drilling operations.
It is to to be noted, with reference to AU 392 143, that said sealing faces are solely located at the outer ends of the sealing wings, i.e. at a considerable distance from the sealing ring stem. By spacing the conic faces of the armature members from the conic faces of the inner portion of the sealing wing over a considerable axial distance the sealing face area is clearly restricted and an intended high moment force is achieved in the sealing face area. Such high sealing forces, when occurring as instantaneous peak pressures in gass or oil drilling pipes, may quite often cause permanent deformation of the sealing ring and a following leaking that will require shifting of a destroyed sealing ring.
By clamping together the stem of the T-shape in the axial direction the sealing ring is locked in place in the intended use position, that is to say in an intended immovable use position. At the same time by arrangement of the sealing flaps in a sealing abutment against the armature members, the seal is precisely set in the immovable use position. Consequently the metallic sealing ring becomes locked in an immovable engagement with the respective armature members.
According to NO 178 388 the metallic sealing ring becomes subjected, during mounting, to an extremely high clamping pressure, so that the sealing ring becomes permanently deformed, that is to say by means of a clamping pressure which involves exceeding the yield strength of the metal. The metallic sealing ring becomes permanently deformed both in an axial and in a radial direction. During use in a pipe conduit any relative movement between the sealing ring and the adjacent armature members is consequently prevented, independently of which tensile or pressure forces which have an effect axially through the pipe coupling. In practice the function of the sealing ring will depend totally upon the sealing ring and the armature members being held the whole time in permanent clamping engagement with each other under a continued high clamping pressure. This function is ensured as long as the extremely high clamping pressure is maintained. On relief of the extremely high clamping pressure which is applied on the pipe coupling the sealing function is made inactive. This involves, during use, on extreme loads occurring axially though the armature members, in combination with varying extremely high internal medium pressures and/or significant temperature variations in the coupling pieces and the sealing ring, a breakage of the seal arising, with leakages following from this and also the need for repair. The repair which makes it necessary to scrap the permanently deformed sealing ring, and possible damage, which is imposed on the coupling pieces, is rather time-consuming and rather expensive. This is particularly the case on use in a pipe conduit which is utilised in a drilling operation and/or in connection with transportation of gas/oil products from wells in the ocean.
In NO 303 150 a sealing arrangement is proposed for the afore-mentioned purpose, that is to say for use in a pipe conduit with associated pipe coupling during extreme conditions of use. In the sealing arrangement the aforementioned metallic sealing ring is omitted. Instead two armature members (coupling pieces) are employed, which form a direct sealing abutment with each other in a mutual sliding abutment via a conical sealing face of an elastically yielding ring portion of the one armature member. There is employed a conical supporting surface of a robust supporting portion of the other armature member. As a result of the slidable sealing engagement between the armature members, in combination with the elastically yielding sealing portion of the one armature member it is possible to ensure an effective sealing engagement during use of the pipe coupling.
This sealing effect can be achieved, even when extreme axial tensile and pressure forces occur between the armature members and even when significant temperature variations and extreme pressure variations occur in the pressure medium which passes through the pipe coupling. Normally the sealing arrangement can be reemployed after use, that is to say after the introductory applied clamping force is relieved.
However, also according to NO 303 150, there are employed very high clamping pressures (up towards the yield point of the metallic sealing portion of the coupling) during mounting, that is to say during the joining of the armature members, and also during the use itself of the pipe coupling. This is caused by the relatively rigid and relatively thick-walled sealing portion of the one coupling piece, which is to be subjected to elastic deformation.
By virtue of the different loadings, which occur in the pipe coupling during use, in combination with the slidable seal which is obtained between the armature members, there are employed in the known solution particularly high clamping pressures, that is to say as mentioned clamping pressures of an order of magnitude almost up to the yield point of the metallic material of the armature member having the elastically yielding sealing portion.
In the known solution the clamping pressure, that is to say the applied preliminary pressure, shall during use be able to compensate for occurring tensile forces and relative axial movements following from this between the sealing face and the stop face of the two armature members, at the same as an effective sealing off is ensured between the armature members.